<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<meta name="viewport" content="width=device-width, initial-scale=1.0">
	<title>Document</title>
	<style>

		.div3 {
			height: 100px;
			width: 100px;
			background-color: green;
			border: 1px solid black;
		}

		.div4 {
			height: 100px;
			width: 100px;
			background-color: blue;
			border: 1px solid black;
		}

		.div3 + .div4 {
			height: 100px;
			width: 100px;
			background-color: red;
			border: 1px solid black;
		}

		
	</style>
</head>
<body>
	<div class="div1">
		<div class="div2">
			<div class="div3"></div>
			<div class="div4"></div>
			<div class="div5"></div>
		</div>
	</div>
</body>
</html>